52 Owner and Subscriber are notified when the course passes to ‘Open’
53 Subscriber becomes courses attendee
54 Owner sets minimal quantity of attendees
55 Owner is notified when course transits to Ready
56 Owner starts the course
57 Attendee is notified when owner starts the course
58 Owner finishes the course
59 Attendee is notified when owner finishes the course
60 Attender evaluates finished course
61 Owner can re-ask evaluation